Abstract
Y chromosome and mitochondrial DNA profiles have been used as evidence in courts for decades, yet the problem of evaluating the weight of evidence has not been adequately resolved. Both are lineage markers (inherited from just one parent), which presents different interpretation challenges compared with standard autosomal DNA profiles (inherited from both parents). We review approaches to the evaluation of lineage marker profiles for forensic identification, focussing on the key roles of profile mutation rate and relatedness (extending beyond known relatives). Higher mutation rates imply fewer individuals matching the profile of an alleged contributor, but they will be more closely related. This makes it challenging to evaluate the possibility that one of these matching individuals could be the true source, because relatives may be plausible alternative contributors, and may not be well mixed in the population. These issues reduce the usefulness of profile databases drawn from a broad population: larger populations can have a lower profile relative frequency because of lower relatedness with the alleged contributor. Many evaluation methods do not adequately take account of distant relatedness, but its effects have become more pronounced with the latest generation of high-mutation-rate Y profiles.
Highlights
Melbourne Integrative Genomics, University of Melbourne, Melbourne 3010, Australia; Genetics Institute, University College London, London WC1E 6BT, UK
We focus here on DNA profiles obtained from the Y chromosome and the mitochondrial genome, which are inherited only from the father and from the mother, respectively
A key message is that the high mutation rates of the latest generation of Y chromosome short tandem repeat (STR) profiles have effects that exaggerate the deficiencies of previous methods of analysis, but understanding these effects highlights ways forward
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. We focus here on DNA profiles obtained from the Y chromosome and the mitochondrial genome (mitogenome/mtDNA), which are inherited only from the father and from the mother, respectively. Because of this uniparental inheritance over generations, these DNA profiles are called lineage markers. The mutation rate of even the whole mitogenome is lower, but insights from the high-mutation-rate setting are informative for evaluating and communicating the weight of evidence. DNA profile (either Y or mitogenome) obtained from an evidence sample, and a matching conditions of the Creative Commons. Reference profile from a known individual Q who is alleged to be the source of the evidence sample (sometimes Q is called the person of interest, PoI). The denominator of (1) is a probability for the unknown profile of X, given the observed q and possibly a database of profiles
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